In general, an electromagnetic flow rate control valve comprises a circular cylindrical solenoid which generates magnetic field when electric current is supplied thereto and a mover which moves in the axial direction under the effect of electromagnetic force when the solenoid is magnetized. The mover is located in an internal space of a housing and normally, it has a circular columnar configuration. The circular columnar mover has closed first and second chambers which are defined in opposite end portions thereof. In case of a valve for controlling the flow rate of fluid, the fluid enters the internal space of the housing where the fluid fills the first and second chambers which are defined in the opposite end portions of the mover. Thus, in order to make it possible for the mover to move smoothly without encountering resistance, there is provided a passageway in the mover, which passageway intercommunicates the first and second chambers.
Problem(s) to be Solved by the Invention
A flow rate control valve of the type just mentioned above can be applied to a wide range of technical field. In one application, the flow rate control valve is used with the axial direction of the valve displaced from the perpendicular direction. For example, in case the flow rate control valve is used in a diesel engine of a vehicle, the valve must be placed with its axis held in a horizontal or semi-horizontal state because of its positional relation with the pump driven by the engine. The moving mover is supported at a plural spots, normally at two spots, which are away from each other in the axial direction. Thus, there is such a fear that sliding wear (uneven wear) occurs especially at the contact area of the supporting points, thus making it impossible for the mover to slidingly move in a correct manner. Moreover, in some instances, the mover must be supported in a cantilever fashion, namely, supported at one spot in the axial direction. Here again, there is a fear that uneven wear occurs. If such a situation should occur, the correct flow rate controlling would be interrupted. In addition, in case of a common rail system (pressure accumulation type injection system), for example, inferior pressure controlling would occur with a result that foreign engine noises are generated. With respect to a flow rate control valve and a common rail system of the type as just mentioned above, reference is made, for example, to Japanese Patent Application Laid-Open No. H11-94097 and Japanese Patent Application Laid-Open No. 2001-221130. As shown in those Laid-Open publications, a fuel injection system including a flow rate control valve of this type (i.e., amount control throttle valve) normally comprises a low pressure feed pump for pumping up fuel oil as fluid from a fuel tank, an amount control throttle valve for controlling the amount of fuel oil fed by the feed pump, under the effect of throttling action and a supply pump for boosting the fuel oil, which has been controlled in amount by the amount control throttle valve, to higher pressure by movement of a plunger and supplying the same to fuel injection means. The amount control throttle valve has an overflow valve attached thereto. Therefore, excessive fuel oil is returned to the fuel tank by the overflow valve. As the supply pump for executing a pumping action in accordance with reciprocal motion of the plunger, there can, of course, be listed not only a pump of an axial type explicitly shown in the above-mentioned Japanese Patent Application Laid-Open No. 2001-221130 but also a pump of a radial type as disclosed, for example, by National Patent Publication No. 2001-500593 (corresponding to International Publication No. WO99/02861). Although the above-mentioned uneven wear is more manifest when the mover is placed in a horizontal posture, an ordinary person skilled in the art would know that uneven wear is liable to occur even when the mover is placed in a vertical posture. The reason is that the mover tends to be offset sideways under the effect of electromagnetic force.
It is, therefore, an object of the present invention to prevent uneven wear of a moving mover and to stabilize the controlling characteristics by a valve.
Another object of the present invention is to provide a technique which can easily be put in practice simply by exchanging an existing part or parts.
Further objects of the present invention will become more manifest from the description to follow.
Means for Solving the Invention
In the present invention, a moving mover is positively caused to rotate about its axis so that wear will occur evenly without allowing it to occur locally concentrically. As rotation means for rotating the mover, the inventor(s) of the present invention paid attention to the flow of fluid in the mover which flows from a first chamber to a second chamber, or vice versa, when the mover is in a moving position.
A stroke which a flow rate control valve of this type makes, including a flow rate control valve for controlling an amount of fluid, is approximately several mm to approximately 5 mm (for example, 3 mm) at most. Moreover, the pressure of the fluid passing through the valve is low. In this respect, the pressure of the fluid around the flow rate control valve in question is relatively low in comparison with the fluid, which is high in pressure, in a common rail as an accumulator. Even such low pressure fluid, in fact, flows in accordance with the movement of the mover. The present invention has adopted an original idea in that the mover is caused to rotate by using of a work of flowing fluid.
The rotation means for making the fluid work, rotation force is exerted to the mover by the fluid flowing from the first chamber to the second chamber, or vice versa. Firstly, with respect to a flow passageway which is formed within the mover and for allowing the fluid to flow therethrough, there are provided a passageway portion along the axial direction and another passageway portion crossing with the axial direction. In doing so, rotation force can be utilized, which is generated when the fluid passes from the former passageway portion to the latter crossing passageway portion (or vice versa). Accordingly, in order to generate effective rotation action, it is preferred that a plurality of flow passageways are provided and they are arranged in symmetrical relation about the axis. A single flow passageway, however, may be also employed.
Secondly, it is also accepted that the passageway for flowing the fluid from the first chamber to the second chamber, or vice versa, comprises a helical groove provided at the outer peripheral surface of the mover. The helical groove may be provided over the entire area from one end of the mover to the other end, or it may also be provided in combination with the passageway within the mover. For example, that portion which supports the mover, may be designed as an internal passageway and the helical groove is formed in the remaining portion which does not support the mover, such that the helical groove and the internal passageway are communicated with each other. Since the fluid passing through the helical groove is increased in so-called length of the arm in moment, it is expected that a larger rotation force is generated. Of course, it is also accepted that the first idea in which the rotation means is provided within the mover is combined with the second idea in which the passageway is provided at the outer peripheral surface of the mover.
Thirdly, it is also an interesting alternative that a spacer disposed at one end face portion of the mover has a function acting as the rotation means. Normally, the spacer at one end of the mover is separated from the mover. This spacer is purposely designed to be integral with the mover at one end face portion of the mover. Moreover, for example, there is provided a slantwise hole extending from the upper surface of the spacer to the lower surface, and/or the spacer is provided with a fan to be formed into a fan type spacer. Then, by passing the fluid into the slantwise hole or fan from the passageway on the side of the mover, rotation force can be exerted to the mover which is integral with the spacer. In the alternative, by providing a cam groove at the outer peripheral surface of the mover and a pin-like cam on the side of a bearing for carrying the mover, rotation force can also be exerted to the mover.
As in the present invention, it is desirous to provide a construction or supporting form which is designed such that the mover itself can rotate easily when it is required to be rotated. In this respect, a mover including a flow passageway which is offset from the axis, is not desirable because its gravity is offset from the axis. It is preferred that a plurality of flow passageways are provided, the mover is constructed in such a manner as to be symmetrical about the axis and the location of the gravity of the mover is aligned with the axis (i.e., center of rotation), so that the mover can rotate smoothly.